Marginal Artery of Drummond Masquerading as a Fistulous Tract Resulting in Recurrent Lower Gastrointestinal Bleeding

ABSTRACT Lower gastrointestinal bleeding (LGIB) can be caused by a variety of causes. Pseudoaneurysms have been described as a rare etiology of LGIB and are associated with pancreatic pseudocysts that involve adjacent vasculature. Our study describes a 38-year-old man with recent severe coronavirus disease 2019 and necrotizing pancreatitis presenting with hematochezia and blood clots by gastrostomy-jejunostomy. Initial flexible sigmoidoscopy did not elicit an etiology for the LGIB. Recurrent hematochezia prompted colonoscopy and angiography, which demonstrated a pseudoaneurysm in the marginal artery of Drummond as the source. Our case highlights the importance of repeat evaluation of gastrointestinal bleeding of unknown etiology.


INTRODUCTION
The mortality rate of patients hospitalized with lower gastrointestinal bleeding (LGIB) has been reported at 1.1% in the United States from 2005 to 2014, which has decreased from previous years. 1,2Various factors have been shown to increase mortality risk from this condition, including multiple comorbidities, age greater than 70 years, male sex, bleeding from a separate process during hospitalization, coagulation defects, hypovolemia, and anemia requiring blood transfusion.4][5] Our study describes a rare case of recurrent LGIB diagnosed as a pseudoaneurysm by endoscopy and angiography.

CASE REPORT
A 38-year-old man presented to our hospital from a long-term care facility with hematochezia and blood clots by gastrostomyjejunostomy.He had recently been hospitalized for severe coronavirus disease 2019 with a complicated hospital course in the intensive care unit including necrotizing pancreatitis with an abdominal drain, multiple secondary infections, tracheostomy, and percutaneous endoscopic gastrostomy-jejunostomy.During that hospitalization, he was found to have a pseudoaneurysm of the gastroduodenal artery on computed tomography angiography after a large bloody bowel movement and subsequent drop in hemoglobin.He received embolization of the gastroduodenal and gastroepiploic arteries at that time.He was also diagnosed with hemophagocytic lymphohistiocytosis (HLH), which was confirmed on bone marrow biopsy and responded to dexamethasone.
During transport to our hospital, he was noted to have tachycardia with hypotension requiring norepinephrine and was transfused 1 unit of red blood cells.Hemoglobin was 7.5 g/dL after transfusion.Esophagogastroduodenoscopy was completed and showed a gastrojejunostomy tube in the expected location but was noted to be tight to the mucosa, which was pale in appearance.Flexible sigmoidoscopy revealed localized areas of edematous and erythematous mucosa with some associated oozing throughout the sigmoid colon.A full colonoscopy was not completed because of the presence of solid brown stool beyond 70 cm from the anal verge.There was no elucidated source for upper GI bleeding that would have explained the blood clots initially found in the gastrostomy-jejunostomy. Computed tomography angiography was completed and did not find an etiology of GI bleeding at that time.There was specifically no evidence of diverticulosis on computed tomography imaging before or after this workup.The patient's blood counts began to improve, and he continued dexamethasone therapy for HLH.
Repeat evaluation was completed 1 week later because of recurrent hematochezia.Colonoscopy was performed with identification of an apparent fistulous tract with active oozing of blood in the sigmoid colon located at 35 cm.There was a moderate amount of bright red blood in the sigmoid and rectum.Endoscopic clips were placed for identification by interventional radiology with the plan for further evaluation by their team.Angiogram completed by interventional radiology localized a pseudoaneurysm arising from the marginal artery of Drummond just proximal to its anastomosis with the ascending branch of the left colic artery and was successfully embolized (Figure 1).Of note, imaging throughout this time had shown similar severe sequelae of necrotizing pancreatitis, including a multiloculated abscess centered within the pancreatic parenchyma.The component posterior to the spleen showed a possible communication through the left hemidiaphragm to a left lower lobe lung abscess.There were also smaller abscesses within the left posterior pararenal space.
After the embolization, the patient had another acute decrease in hemoglobin caused by a ruptured mesenteric pseudoaneurysm.He had continued to have a clinical decline, including intermittent hypoxia requiring manual bagging and worsening hypotension over several days.After worsening desaturation despite manual bagging, the patient's family ultimately decided to transition to comfort care.

DISCUSSION
Pseudoaneurysms, such as the one described in this case, have been associated with pancreatitis and can result if a pseudocyst involves adjacent vasculature. 6Although rare, it has been seen in up to 10% of patients with chronic pancreatitis. 7I bleeding has been reported as a rare presentation of this condition. 8,9This case highlights the importance of repeat endoscopy and angiography in the setting of a GI bleeding of unknown etiology.
Pseudoaneurysms are most commonly asymptomatic but may also present with epigastric pain or GI bleeding. 4,8,9GI bleeding, although a common phenomenon, is associated with high morbidity and mortality. 2In cases of pseudoaneurysms, bleeding may be intermittent and insidious and can lead to significant blood loss. 8,9Given the anatomical location of the pancreas and surrounding splanchnic vessels, bleeding may occur in the bowel, peritoneal cavity, pancreatic duct (hemosuccus pancreaticus), or biliary tree. 10,11Hemosuccus pancreaticus is bleeding in the pancreatic duct through the ampulla of Vater into the duodenum and is an extremely rare cause of GI bleeding associated with pseudoaneurysms. 11,12In other cases, pseudoaneurysms have been mistaken for malignancy or even carcinomatosis peritonei. 13veral case reports have reported mycotic or fungal aneurysm formation in association with HLH. 14,15Given that cytokine storm and a marked proinflammatory state are central to the pathophysiology of HLH, further investigation is needed to determine whether HLH predisposes patients, such as ours, to aneurysm/pseudoaneurysm formation. 16eudoaneurysms prove to be a diagnostic challenge with great heterogenicity of presentation. 3,4,8,9Angiography is useful in identifying sources of bleeding and has been used frequently in locating pseudoaneurysms. 3,4,9As with other GI bleeds, management should prioritize identification of the source and transfusion if needed. 13Embolization serves as the definitive treatment for these cases. 3,17,18his case report of pseudoaneurysm of the marginal artery of Drummond after a case of necrotizing pancreatitis presenting with recurrent bleeding highlights the importance of considering pseudoaneurysm formation as a differential of GI bleeding in the correct clinical situation to prevent recurrent procedures and further complications.

Figure 1 .
Figure 1.Digital subtraction angiogram with a catheter selected in the ascending branch of the left colic artery demonstrating the pseudoaneurysm (arrow) present immediately distal to the anastomosis with the marginal artery of Drummond.